Abstract: We seek to use a novel cell-internalization SELEX (Systemic Evolution of Ligands by Exponential enrichment) to isolate thioaptamer-conjugated liposomal nanoparticles (TA-NP) that internalize and deliver its siRNA into the cytosol of tumor initiating cells (TIC) of oral squamous cell carcinoma, minimizing off-target delivery. In vivo delivery and release of siRNA from the endosomes to cytosol remain the two biggest obstacles for translating anticancer siRNA drugs to the clinic. Oral squamous cell carcinoma commonly known as oral cancer (OC) is the most common malignancy of head and neck with high global public health impact. Fanconi anemia (FA) is a hereditary cancer syndrome that predisposes one to OC. Evidence points to TIC as the key driver of field cancerization, resistance to therapy and disease relapse. A therapeutic vehicle that selectively targets and delivers anticancer drugs to TIC offers great promise for OC treatment. Our data and published studies show: (1).TIC is more enriched in FA-OC than sporadic OC; (2) Chk1 and CD147 promote TIC survival and chemoresistance and its overexpression contribute to poor prognosis in OC. The main goal of this proposal is to use FA- OC-TIC as target cells to develop TA- NP for the cytosolic delivery of siRNA. We hypothesize that isolated TA-NP will facilitate targeted delivery of siRNA to OC-TIC cytosol, and silence CD-147/Chk1 in OC-TIC's, disrupting their niche and rendering them chemosensitive and susceptible to elimination by chemotherapy with gemcitabine. Aims:(1): Elucidate the effect of RNAi mediated silencing of CD147/Chk1 in FA-OC-TIC; (2A): Select a list of TA-Liposomal NP (TA-NP) specific for TIC fraction of FA-OC cells, while avoiding hepatocyte uptake, using a positive and negative cell-uptake based SELEX; (2B): Determine the selected TA-NP's targeting specificity and therapeutic efficacy in in vitro and in murine OC xenografts. We will isolate ALDH+ TIC in FA-OC cell lines and examine the effects of siRNA-mediated silencing of CD147 and Chk1. (2) We will use a modified conjugate SELEX with positive and negative selections to identify OC-TIC-specific internalizing TA-NP. (3) We will validate TIC-targeting specificity and silencing efficacy of isolated TA-NP-sRNA in vitro and in murine orthotopic FA-OC xenografts. RNAi mediated inhibition of CD147 and Chk1 in OC-TIC will yield valuable insight into their potential role in the tumor propagating and chemoresistant properties of OC-TIC. The proposed TA-NP will have important clinical potentials for in vivo delivery of therapeutic and imaging agents targeting the OC-TIC.